What is different about how lenie killed the pup what does this change about lennies character?

In "Of Mice and Men," Lennie kills the pup accidentally by petting it too roughly, unlike his intentional killing of Curley's wife. This accidental nature of the pup's death highlights Lennie's innocence and his inability to understand the consequences of his actions, emphasizing his childlike mentality and vulnerability. It adds complexity to Lennie's character as it underscores his lack of malice and his struggle to comprehend the world around him.